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-57v on tube5 Pins 1 & 5
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The "bias pot" you refer to in post #11 is actually not a bias pot but rather is for tubes matching or also called hum balance. If it is cranked all the way to one side, it might account for the difference in bias voltage between the two tubes."I took a photo of my ohm meter... It didn't help." Enzo 8/20/22Comment
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Thanks Dude
bias voltage is now correctly
Chuck ... no DC on preamp tubes
bias balance is set at -47
PI cathodes 114v
PI grids 72v ( is 72v correct ? )Comment
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72V for the grids is not correct. The cathode voltage should only be about two to four volts higher than the grids. Did you check the value of the PI cathode resistor?"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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That ^^^^^^. Then, if you don't have DC on the filaments after plugging in the preamp tubes, I'd say you're safe to put in the output tubes and give it a whirl. After you confirm everything is working correctly, you can adjust the hum balance for minimal hum."I took a photo of my ohm meter... It didn't help." Enzo 8/20/22Comment
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Just be sure and re check for that DC on the filaments after the power tubes are plugged in. The amp should not be operated, even for testing, with a tube that shorts DC to the filament circuit.Originally posted by The Dude View Post"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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Cathode resistor is 485Comment
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You can't measure the grid voltage on the LTP PI with a meter directly. The high value grid resistors and the meter impedance form a voltage divider that reads the voltage REALLY low. The grid voltage is unlikely wrong anyway. The only way to measure it is directly from the cathode or at least from the bottom of the cathode resistor - in other words across the grid resistor. So if the cathode measures 100v, and the grids 72, that is probably right. measure the grids from the cathode, and they will only be a volt or two removed.Education is what you're left with after you have forgotten what you have learned.Comment
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Chuck ... I will recheck for DC on filaments after power tubes are in BEFORE I operate amp.Comment
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Good call! I missed that. I know it happens, but I missed it anyway. Good thing it's not just me responding to this thread
"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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Oh, it is just you. I am only a fig newton of your imagination.Education is what you're left with after you have forgotten what you have learned.Comment
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Well, let's fire this darn thing up then!
"I took a photo of my ohm meter... It didn't help." Enzo 8/20/22Comment
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Well, no explosions here in California, so that's good.
Bass channel has no volume until 4 and on 10 sounds like 1/4 volume
Normal channel is dead as a large door nail
making progress
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Just checkin'. You don't have all of the tone controls all the way down do you?"I took a photo of my ohm meter... It didn't help." Enzo 8/20/22Comment
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And no DC on the heaters?"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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